Sorry for the long thread title but it really is the entire premise of the thread there. If this has been done please ignore, I searchbarred it but didn't find anything.
American History X:
The end obviously when Ed Norton is in the doorway looking into the bathroom and breaking up. Really the way the film cuts out basically right then is what makes it so powerful cause you saw his character go from this extreme racist to this rather normal person that realizes what he once believed is wrong. It leaves you hanging what happens to his belief system after.
The Guardian:
When Kevin Costner is being held by Ashton Kutcher and is told "I won't let go" and he just responds by saying "I know" and reaches up and unbuckles his glove and allows himself to fall into the ocean.
We Were Soldiers:
The very end before Mel Gibson goes back to the States when they are standing there trying to recover their dead comrades.
Black Hawk Down
When Shugart and Gordon die (the snipers) as well as when Eversmann loses one of his squadmates. I read the book and every time I open watch the movie since it has become less of a "war movie" and a much more seemingly personal movie.
The Bear:
When the bear cubs mother dies right at the beginning as well as when the big male Grizzly gets shot.